Luke 1:27 …to a virgin betrothed to a man whose name was Joseph, of the house of David. And the virgin’s name was Mary.
Luke says Mary is a “virgin”. This is the Greek word παρθένος/parthenos. Let’s focus on a couple of definitions from Strong’s and Helps Word Studies.
Strong’s defines the term as a maiden, virgin; extended to men who have not known women.
Helps states properly, a virgin; a woman who has never had sexual relations; a female (virgin), beyond puberty but not yet married.
παρθένος/parthenos is noted 15 times in the New Testament. Three (3) times the term is used in reference to Mary. The virgin is going to give birth to a child. For Jews of the day, the idea of a virgin giving birth would bring Isaiah 7:14 to mind. Prophecy is going to be fulfilled.
Isaiah 7:14 Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel.
The Hebrew term for virgin is “almah“. Strong’s defines the word as a young woman, a virgin, a maiden. Almah is noted seven (7) times in the Old Testament. It is translated as maid, maiden, or virgin.
Historically, there has been much debate over the meaning of the term almah in Isaiah 7:14. Many Old Testament commentators take the term to mean “the concealed one”.
When the Old Testament was translated from Hebrew to Greek in the Septuagint, almah was translated to αρθένος/parthenos. In both cases (Hebrew and Greek), there is a definite article before both terms. In English, we know this as “the” virgin.
I take it Greek Orthodox scholars understand. See the link below for great detail of linguistic study.
https://www.goarch.org/-/the-word-almah-in-isaiah-7-14
Mary herself makes the claim she is a virgin. Many translators use the term “virgin” in Luke 1:34. The text is literally translated below as…
Luke 1:34 And Mary said to the angel, “How will this be, since I do not know a man?”
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…of the house of David.
The genealogies of Luke 3 and Matthew 1 are clear. Jesus is of the line of David. It does not matter which parent, Mary or Joseph. Both have direct links to David. Luke is making the case. The Child to be born of the virgin Mary is of the line of David. The Messiah is promised from 2 Samuel 7, roughly 1,000 years and 14 generations before the conception of the Child.
2 Samuel 7:8-17 “Now therefore, thus you shall say to My servant David, ‘Thus says the Lord of hosts, “I took you from the pasture, from following the sheep, to be ruler over My people Israel. I have been with you wherever you have gone and have cut off all your enemies from before you; and I will make you a great name, like the names of the great men who are on the earth. I will also appoint a place for My people Israel and will plant them, that they may live in their own place and not be disturbed again, nor will the wicked afflict them any more as formerly, even from the day that I commanded judges to be over My people Israel; and I will give you rest from all your enemies. The Lord also declares to you that the Lord will make a house for you. When your days are complete and you lie down with your fathers, I will raise up your descendant after you, who will come forth from you, and I will establish his kingdom. He shall build a house for My name, and I will establish the throne of his kingdom forever. I will be a father to him and he will be a son to Me; when he commits iniquity, I will correct him with the rod of men and the strokes of the sons of men, but My lovingkindness shall not depart from him, as I took it away from Saul, whom I removed from before you. Your house and your kingdom shall endure before Me forever; your throne shall be established forever.”’” In accordance with all these words and all this vision, so Nathan spoke to David.